too young for night terrors/ nightmares?

ds3 is 2½ and has always been an eractic sleeper. (I'm sure he would've been better if we could've followed his routine!) however last night and tonight he has woken not long after settling quite upset, impossible to comfort, then just goes back to sleep. ds1 still has night terrors and he is 6 but I am sure they started later. any thoughts.